Portsmouth clean air plans: Where does pollution come from?

Portsmouth City Council plans to charge taxis, lorries and coaches without the latest efficient engines up to £50 a day to enter part of the city.

But according to AECOM only a quarter of the nitrogen dioxide and nitric oxide emissions in the city in 2018 came from road transport.

Under the plans, owners of older vehicles registered before 2006 or diesel vehicles registered before 2015 would be charged to drive into the zone.

Privately-owned cars and motorbikes would not be affected.

BBC South Transport Correspondent Paul Clifton explains how the majority of the emissions actually come from shipping.